The presently disclosed subject matter generally relates to improved methods and devices for the analysis of gas phase ions via ion mobility type analyzers, particularly high field asymmetric waveform ion mobility analyzers (FAIMS). FAIMS is a gas phase ion separation technique which utilizes the non-linear change in ion mobility as a function of electric field strength to filter ions (McDaniel and Mason, 1973).
There exists a need to improve the performance of FAIMS. Efforts to improve FAIMS performance, including, for instance: the use of planar geometry FAIMS devices instead of cylindrical devices; increasing the amplitude of the “high” portion of the electric field by improving power supply designs; decreasing the inter electrode distances thereby allowing an increase in the electric field without discharge; using chemical modifiers or carrier gas dopants; and modifying the composition of the carrier gas, have been met with limited success. However, each of the previously attempted methods of improving performance has come with an associated cost. For example, any improvement made to FAIMS performance in the prior art for one compound or class of compounds, by using a modified carrier gas for example, has come with a loss of performance for some other class of compounds. This loss in performance may reduce resolution, reduce peak capacity, or result in a loss of signal intensity. In addition, gas mixtures which contain a gas with a lower dielectric breakdown threshold, or include reactive gases may shorten the operational lifetime of the instrument.
Thus, the need to optimize FAIMS performance, including modifying the carrier gas composition in a compound specific manner in order to improve overall performance, still exists. The presently disclosed and claimed subject matter addresses this and other needs in the art.